How did you create your buttons? Certain types of buttons cannot have their destination property changed. My guess is that your main feature button was created when you dragged the file to play onto the main menu, the chapter button was created when you did an "insert scene selection menu" and the extras button was created by "insert submenu" - how am I doing?

You've got a couple of options for doing transitions; lets start with the main feature. First, delete the main feature button from the main menu, and drag the main feature file from the explorer box into the project tree view. Now select a button from the buttons tab and drag it onto the menu. In the button properties under "action" set the destination to be the transition media that you previously included in the project. If you want a thumbnail from your movie (animated or still) go to the graphics section of the button properties and specify the movie media as the thumbnail. Now, using the project view, navigate into your transition media by double clicking on the icon. Set the end action of the media to link to your main movie.

Now when you click on the button for your feature on the menu, it will go to the transition media which will play and then will take you to the actual main feature when it ends.

Now, a transition for your scene selection and extras. Again, using the project view drag the menus from under the main menu (usually "menu 1") to the root of the project (represented by the DVD). Going back to your main menu, place 2 new buttons on the main menu and label them "Chapter" and "Extras" (or whatever).

Note - if you are going to use the same transition, then at this point you'll need to drag the transition media from the explorer window into the project two more times - I would suggest also renaming these additional instances so that they are easy to identify when you set your link properties.

Ok, going back to the "Chapter" button; set the destination to be the second instance of the transition media. Using the project view, navigate into the second transition media instance and set the end action to link to the scene selection menu.

Repeat this procedure for the "Extras" button using the appropriate instance of the transition media.

Enjoy!
--Scott